The Third Leg
by TurtleFriedRice
Summary: Two mermen get cursed to be human for a short while. Beached and nude, they just cant help but wonder how these bodies exactly work.. Zosan mermaid AU. Smut


Sanji gasped out, turning his head quickly to the side and spitting out sea water. His body was on fucking fire, his head spinning as he desperately tried to breathe. His eyes opened wide, scanning up at the sky. It was different to him this time and he didn't know why, but knew he was about to find out. His back still against the hot sand, he turned his chin, gazing at the face of the figure hovering over him.

Zoro was at his side, he had been for some time, desperately trying to get him to breathe. He tried hitting him, shaking him, everything! Thank god for some reason blowing some air from a kiss did the trick. What was the chance of that? Still, thank god the cook had finally woken up. He wasn't sure how he would even begin to handle the situation if he didn't... Or handle the guilt.

Sanji's eyes scanned his face, trying to recall the reason for alarm other than the fact he'd nearly drowned. He lifted up his hand, lightly brushing his fingers on Zoro's cheek before narrowing his eyes. Then he purposely grabbed a handful of that Marimo hair and ripped it down.

"You shitty Marimo!" Sanji yelled furiously, recalling everything as he pulled himself up, using Zoro's skull as support. "You just had to piss her off didn't you?"

Zoro yelled out, his hands fleeing to Sanji's to finally free himself. Then he growled, scowling at him.

"Oi! It wasn't my fault! Just cause' I wouldn't kiss up to her ass like you did." He snapped back, turning to sit down himself, averting his eyes.

Sanji was still staring with his face down though, rage running through him. "I swear I should fucking kill you-"

He paused, his face paling as his eyes caught sight of the first change. He turned his chin and gazed down at his lower half. It was different. It was... human. He had legs! Fucking legs?! He dared to reach and touch one. It was fleshy, like the upper half of his body, not a scale in sight. How could this have actually happened?

"How..." he squeaked out in his confusion.

Sanji turned to look at the Marimo who was watching him with a guilty expression. His eyes traveled down his body as well, he too seemed to have been transformed, no trace of his mermaid tail in sight or any scales.

"Why...?"

Zoro continued to avoid his eyes. He couldn't handle that defeated and dejected expression of the cooks. After all he had kind of gotten them turned into a whole freaking other species. Dammit he didn't exactly have a choice otherwise! That Shitty wicked queen Kureha was trying to bewitch Sanji. Though unfortunately now here they both were, bewitched and cursed to the land, somewhere they'd never been before in bodies they were not familiar with.

Finally after taking a deep breath to prepare himself, he glanced back over at the blonde, who seemed a little more preoccupied. His expression was still mortified but he'd turned back to inspecting his new body, watching with great concentration at the toes on his feet as he tried moving them. Zoro couldn't help but be a little impressed, as he looked at his own, he could only move the big toe and the... Dammit this wasn't the time to be comparing about who could operate better!

"Cook listen... I didn't mean for that to happen. I just needed to get you out of there."

"It's fine Zoro." Sanji cut his explanation off short.

He was mad, there was no doubt about that. He loved being a merman, it was his pride and he loved swimming in the sea. But he also loved Zoro. It was a big sacrifice, but Zoro would have been punished for his actions regardless. At least this way, though it was horrible to think so, they would still be together even through a curse. But damn was he still mad! He enjoyed at least Zoro's baffled expression at his resolve.

Sanji tried pulling this leg thing back, fascinated with the way he could feel both separately, move both independently, totally different from the power of having just one tail. So while Zoro had finally gotten over feeling guilty and tried standing and walking (And failing to the blondes amusement as he watched in the corner of his eye), Sanji couldn't help but notice something else that was completely different about the human anatomy.

He stared down at this abnormality between his legs. What was this used for? In all the pictures of humans he'd seen back home he'd never seen any mention of this. Though they also seemed to wear unusual garments made out of smothering cloth... Though he didn't see any of that really lying on the beach for them to wear. Still his eyes drew back to it. How strange. Even Zoro, who was falling on his face for the fifth time after somewhat getting it, had one. What did they do?

Zoro pulled himself out of the sand and scowled at the chuckling cook. The fuck did he have to laugh about? He wasn't exactly trying to make the most out of the situation and try this 'walking' thing. Instead Zoro crawled over closer, using the strength of his elbows to pull him through the sand. He pulled himself up halfway, furrowing his brows at where Sanji was staring. It was one thing to think Zoro was a little absentminded, but perhaps he was because he hadn't really acknowledged this appendage either.

"The fuck is that?" He finally asked, turning himself on his backside so that he too could stare at his.

Sanji shook his head, glancing over at Zoro's. "I don't know." he confessed. "Some third leg, maybe?"

Zoro shrugged but still didn't look convinced. "Why's mine bigger? Is that... good?" He grinned. "Like fin size?"

Sanji rolled his eyes. "I doubt it's like that you shitty Marimo. Humans are more primal so... it could be anything so- ah."

Zoro's eyes widened a little in concern, watching as something twitched passed Sanji's face that made him gasp out.

"Oi? What's wrong? What's happening?"

Sanji held his breath, staring down at this long member attached to him. He had tried to barely touch it, much like he had felt his legs for the first time, but something had shot up through him. It was alarming, opening his senses and he wasn't quite sure why.

"I..I don't know. That felt really weird." He admitted, a red tint starting at his cheeks.

Zoro glanced down at his own again. Touching this leg was weirder than the others? Of course he couldn't not try it. Though perhaps, he didn't have to be so rough with his calloused hand, going for a squeeze. He practically yelped out, alarming the blonde.

"You moron! The fuck did I just say, don't touch it! It's.. doing something!"

Sanji was right. Much to both their fascination, something was happening to Zoro's. It was staring to harden, shifting. His expression was priceless, his own face flushing at his confusion as he looked over at Sanji pleadingly.

"What should I do? What's it doing?! Oi, Cook!"

Sanji was speechless... He didn't know what to say to Zoro because... He wasn't doing so well either. Somehow from just watching Zoro's change, his had began to as well, but it was slow and gradual. He swallowed thickly.

"Zoro.. this feeling.. when you touch it, you feel it too right?" He asked, moving to stroke his own just to make sure he still felt it. It made him groan through his teeth.

Zoro rolled his shoulder's a bit. It felt so long now since he had heard the cook last groan and for some reason he found it much more intoxicating. Still he wanted to be able to provide the cook with the answers he wanted, growling as he stroked himself again. He knew they were confused and didn't know why their body was reacting this way, but that unusual feeling that sent shivers through his body was beginning to actually feel good. Really good actually, like he wanted, no needed to do this some more.

"Cook.. I think we're suppose to do this." He muttered finally, starting temptingly at his own. "Look how it's reacting, it's gotta be normal."

Sanji slowly nodded. He was feeling the same feels as well after all. So, under the impression they were trying to make a discovery, they found themselves touching this unknown limb, watching in fascination and lust as it began to stiffen and rise. It didn't help when something crossed Sanji's mind that he could not put aside.

"I dont..." he panted softly. "Understand why they would need something like this..."

Zoro shook his head. Hell he didn't know either. Why couldn't he pull his hand away.

"Fuck I think I feel it.. throbbing or something..."

"What? Let me feel..."

Sanji slowly shifted himself closer to Zoro, ignoring the fact he could practically feel his lover's deep breathing across from him. Still, he reached over, lightly stroking Zoro's and watching as the swordsman visibly shuddered, closing his eyes at the touch. It was such an amusing display coming from the tough Marimo, he couldn't help but do it again and harder. Damn, it was exhilarating and nerve wrecking at the same time. As he touched Zoro, it was like he to was being touched, his body working up.

Until a sudden urge seemed to come over him. He froze and pulled back immediately, staring at the Marimo will a blank face.

"Marimo I think I know what this is..." He spoke nervously.

Zoro seemed pouty still, a little bothered Sanji had stopped his earlier experimenting. Still, he was just as curious.

"Shoot."

"I think... that this... is something humans use to mate."

"Huh?"

"I mean.. that's what it feels like! Can't you tell? It's just weird its like.. when we're courting...but more alive."

Zoro still seemed skeptical, gesturing back to his now full hard-on.

"But look at it. What are we suppose to do with this?" he asked breathlessly.

Sanji pursed his lips a moment, trying to think before finally proposing. "Do you see a hole anywhere...?"

It was the most logical explanation due to it's size and shape that Sanji could make out at least. He'd seen some dolphins do it that way once. And though humans weren't anything like dolphins and nothing like mermaids, he couldn't be sure. There was also the fact of gender differences between humans. From what he could recall when humans had been mentioned in their studies, back when they were in school, there were major gender differences between humans as well. What if, one of them wouldn't have this hole, should there be one?

Sanji might have regretted saying anything though, the way there seemed to be a glint in Zoro's eye. Of course at having that mentioned he would want to just try it. He jumped up onto his knees, having gotten a better hold on balancing with them and leaned in toward Sanji, grinning into his face.

"Oi cook, let's try human sex." was the first thing that came to mind.

Sanji felt his face grow warmer. Was this guy a moron?!

"You idiot what did I just say about there being a hole- Oi!"

Zoro grabbed Sanji's new legs, the ones the blonde still hadn't mastered enough to kick him away with and spread them apart, looking down excitedly at what he could see.

"There is a hole. See, it's right here, don't you feel it?"

Sanji tried to arch his back and look to no avail. It was only when Zoro purposely put the top of his finger inside that his eyes widen and he knew.

"I-I have the hole?" He mumbled quite disappointingly. He though he'd be at least the male of this species too!

Zoro's grin grew wider. "Come on. Let's try it. We'll be doing it a lot like this anyway."

Sanji studied Zoro's face, swallowing thickly again. Logic in his head was screaming no, that they didn't know enough about these bodies and it wasn't a good idea. But his erection, still throbbing painfully at being neglected, was persuasive. He wanted it, he wanted to try.

"A-Alright. But Marimo if I tell you to stop-"

He was cut off by the sound of his own moaning out, painfully. Zoro had brought himself in close and without any warning, began pressing his way inside. He groaned out, this feeling of tightness around him and heat intensifying. What the hell was this? God why did he want to go in deeper? His hips bucked, causing tears start up at the blonde mermans eyes from sheer raw burning pain.

Sanji's body trembled. He felt like he was being split apart at the base. How was this sex? How was this pleasurable? Fucking humans! This is not what he wanted.

"Zoro! Pull out! Take it out now! It's not suppose to go in there!" he yelled, biting down hard on his lip, feeling everything as the swordsman bucked against him again.

Zoro, wasn't so convinced though. Even though it was mildly uncomfortable, being as tight as it was, he couldn't help but have this urge to thrust and go deeper. He shook his head.

"No Sanji, I think this is right. I think I need to keep moving inside."

He rocked his hips, pressing into Sanji again, the sound of Sanji's vocals at his ears not frightening as they would usually be since they were screams, but encouraging.

"Oh god, Marimo! Listen to me!" Sanji moaned out.

He was protesting to deaf ears. His body betrayed him though, seemingly knowing more than he about this process. Was it acting naturally on its own? So human sex was like this? Still it tightened around Zoro, attempting to draw him more inside, to fill this void inside the blonde.

"Relax cook, fuck! Make it relax!"

Sanji closed his eyes tight. How the hell was he suppose to even do that? He hadn't exactly even learned how to walk! Still he tried his best, abling the Marimo to try and move again. But as Zoro continued, thrusting in here and there, the pain actually began to dull and ease after time, something about it becoming easier to thrust. He dared to look down at himself inside Sanji, noticing the faint trail of red staining him, but still he continued, assuming it normal. He was getting into it now too, as Sanji's yells were getting less intense and his hips bucked to inform him things were getting slightly better on his side as well, moving faster and trying to get the perfect fit.

"How long," He began to growl through clenched teeth. "Do you think it takes?"

Sanji was covering his face with his arm, trying to focus on what was being done to him. So many feelings running through him, it felt like he might actually burst and soon, but he didn't know from what. It didn't help when in one of Zoro's thrusts, something happened neither were expecting. A power ran through Sanji so great he almost lost it. And what was scary was it actually felt good, causing him to become much vocal again.

He looked up at Zoro's eyes, which were wide in panic as he felt he might have hurt him yet again, but Sanji's expression was different.

"What the hell was that?!" He asked wildly, looking down Zoro's body where he was working. "Do it again."

Zoro was anything but obedient, certainly so if it meant Sanji had figured something out about this species sex. Keeping the same angle, he continued to thrust back in, a little harder these times to ensure the cook felt it.

And he did, the way it made his curls curl and his back arch.

"Oh shit! It's happening! I can feel it." He managed to gasp,

Then it happened. Sanji's vision went white and his body shuddered, a euphoric feeling rushing over him and something that had been built up had been released, splashing up between him and Zoro, dirtying the sand and he was yelling louder than before.

Before either could realize what was happening, Sanji to lost in this extreme feeling, his body tightened around Zoro, proving any future movements difficult. The swordsman tried, though confused by the sudden sight of white liquid shooting between them as whether or not he should. Even so, the cook's body wrapping around him tighter as he felt Sanji go through his orgasm had him too experiencing the same thing.

His head fell back and he groaned out Sanji's name, the only thought on his mind as he wondered if he was experiencing this rush and overwhelming feeling as well. His pressure built up released from inside him, deep into the cook as his body quaked. Then all was silent but the deep panting of their breath.

Sanji was laying back in the sand, limp with his face to the side as he tried to recall what the hell they had just experienced. What was that? Had that been the sex? He liked it, but at the same time he was unsure. His backside still ached something fierce.

"Zoro... I think its over.. get out of me." he finally said.

Zoro was trying to clear his thoughts as well, his face shadowed as he had no idea what had come over him. He pulled himself out, hissing at the feeling still and watching as his released substance, traced with another that was a shade of a more crimson red, trailed out with him onto the sand. Frustratedly he tried getting the substance off with his hand, only to give up.

Finally the blonde, still a bit shaking from the invasion of his new body, propped his head up and with his hand felt the odd transparent substance on his chest. It mirrored what their release as mermaids looked, but something about it was different and unusual, even unlike how he imagined human's to be. Still, at least it confirmed that they both had had this human 'sex'.

"So this is.. their seed?" the cook mused out loud, but not asking anyone in particular.

He had just had human sex after all, topped by Zoro who apparently was the human male. It had been exciting, pleasurable and frightening all at the same time, but they'd done it. It was territory that no doubt no human had gone to before.

Zoro was still quite for some time, contemplating this before looking back at his lover.

"It wasn't... bad though, right? A lot more intense than courting." He tried to defend, should Sanji be upset in someway.

Sanji stared at him a moment before putting on a weak smile.

"Yeah, it wasn't bad.. like you said, we'll be doing stuff like this for a while so.. probably better we learned now, eh Marimo?"

It warmed Zoro's chest a bit to learn he wasn't in the dog house about this.

"Now you just gotta learn how to walk cook."

Sanji groaned out, falling back. He felt so sore and exhausted some how, he didn't want to even try and get up and walk after that. His back side hurt like nothing else, which he assumed was probably because it was their first time, but still a bit uncomfortable none the less.

"Ugh you shitty moss head I am not in the mood for that right now-"

He stopped though when he saw Zoro getting up for the millionth time. He too had this hole on his backside. Zoro looked at him curiously since he hadn't finished his sentence, turning his heard slightly.

"Eh?"

"You have one too. A hole."

The Marimo tried looking over his shoulder, going in a lame circle before reaching back for a feel. He touched it a moment, his eyebrows furrowing as he tried to feel it like Sanji had, then frustratedly looked to his cook. There was a determination in his eye.

"Oi. Let's try it again."

* * *

**Author's Note: Sorry this wasn't beta'd! I love Zosan mermaids, did you know that? No. Well I do. They are so innocent and fun *^*/ inspiration from this came from a discussion about said zosan mermaids with my dearest Mitsu and friend Nyuu**


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